Smith and colleagues radiocarbon-dated samples of seeds in soil collected in the 1960s from middens, or garbage piles, of the Riverton culture.
In communities of about six to ten families, the Riverton people prepared their food without ceramic pots or boiled water: The families broke nuts, ground food on slabs, and used earthen ovens with fire-heated rocks.
They likely ate sunflower, marsh elder, two types of chenopod—a family that includes spinach and beets—and possibly squash and little barley, according to the findings. The people also grew bottle gourd to make into containers.
Several of these "aggressive" colonizer plant species, such as sunflowers and bottle gourd, are around today, said Smith, whose research appears this week in the journal Proceedings of the National Academy of Sciences.
Many of the Riverton plant species are so hardy that modern gardeners in the U.S. Midwest or Southeast often find them stubbornly popping up in their backyards, he said.
Icing on the Cake?
The Riverton crops may have "added to what was [already] a successful life" for the ancient Americans, said Brian Redmond, curator and head of archaeology at the Cleveland Museum of Natural History in Ohio.
But that doesn't mean farming didn't give the Riverton culture a practical advantage: In addition to their normal fare, the people may have relied on the crops as a stable source of food—insurance against shortages of wild food sources—Redmond added.
The Riverton discovery, he said, "gives us a whole lot of dimension to what these people are doing in this time."
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